1. Field of the Invention
The present invention relates to a bar code reader which irradiates laser light onto a symbol such as a bar code, receives reflected return light, and reads information from the symbol.
2. Description of the Related Art
Generally, the bar code is read by the bar code-reader to generate recorded information. The bar code-reader irradiates laser light from a laser light source such as a laser diode (LD) for scanning, and receives reflected return light (reflected light) including information by a light receiving element such as a photo-detector (PD). A light receiving element generates a detection signal after photoelectric conversion of the received return light. The detection signal is decoded and recognized as information.
A user directs the bar code reader toward a bar code to be read, to irradiate laser light thereon. In a case in which other unnecessary ambient light caused by an in-situ environment, for example, illuminating rays and sun rays are mixed into the return light when the return light is received, there is caused a situation in which larger noises are generated and information may not be correctly read. For example, Jpn. Pat. Appln. KOKAI Publication No. 2002-183658 has disclosed a configuration as a bar code reader preventing the above situation. According to the configuration, there is provided a light shielding portion covering a range except a light receiving surface (through hole). Moreover, laser light emitted from a laser diode is polarized into parallel light flux through a collimator lens and is formed into a thin beam by a diaphragm portion for irradiation according to the above configuration. The above bar code reader correctly reads information by a configuration in which small-diameter laser light is irradiated by providing the through hole and the diaphragm portion, and other unnecessary ambient light is prevented from entering.
Moreover, a smaller and lighter bar code reader with a module structure has been manufactured along with development of technologies, and various kinds of electronic devices such as a portable device with a wireless communication function have been equipped with the bar code reader. For example, U.S. Pat. Nos. 6,360,949, 6,303,927, and the like have proposed such an electronic device.
The above U.S. Pat. No. 6,360,949 has tried to modularize a laser scanning optical system called a retro collective system. That is, according to the system configuration, laser light is emitted using a plate mirror for scanning, and return light is taken into a photo-detector using a light condensing mirror. A smaller size is realized by returning incidence light by the use of two mirrors.
U.S. Pat. No. 6,303,927 has disclosed a configuration in which return light is taken into a photo-detector, using not a light condensing mirror but a light condensing lens as a light condensing element. There is an arrangement in which the light taken into the detector is deflected through about 90° by a scanning mirror, and is directed from the light condensing lens toward the photo-detector. An object of this technology is to realize higher-performance reading by a configuration in which the light condensing lens is arranged in the vicinity of a scanning aperture in parallel to the laser light source.
When the size of the scanning mechanism is made smaller and modularized as described above, for example, a portable terminal with a wireless function may be equipped with the mechanism. As a result, inspection processing and object authentication may be automated even outdoors, and in a mobile unit such as an automobile and an airplane in which the scanning mechanism has not been used so far. Accordingly, the scope of application of the product may be extended, and the convenience may be remarkably improved. Such a bar code reader has been widely used in home delivery service, logistics service, a food industry, and the like under a state in which a portable terminal is equipped with the bar code reader. Moreover, application to, for example, an inter-vehicle sensor, a safety and crime-prevention device, and the like may be also realized by applying the modularization technology to an object recognition sensor and the like.
When such a smaller and lighter reader with a module structure is realized, various kinds of examinations have been made in order to realize higher-performance reading, and to execute assembly work, inspection processing, and adjustment operation in an easier manner.